I’m facing a similar issue with Vikunja. My Authentik instance was wiped, and now all users have different UUIDs. When users log in via OIDC, Vikunja creates a new user account, even if the email address is the same. I do have both usernamefallback: true and emailfallback: true enabled, though. An option like that to merge accounts and overwrite the local uuid of the user in the vikunja db would be much appreciated.